With the current issue of the magazine having topics regarding Data Access I thought I’d cover both software data access and how people access data via the web.

Lost in Translation

You may remember me writing about UMN MapServer, what I believe to be the best Open Source Internet Mapping engine available.  Close to the heart of this software is a package known as OGR which allows MapServer to read over 125 vector and raster formats natively i.e. Oracle Spatial, MapInfo TAB, Microstation DGN , ESRI SDE & Shape and many more.  I believe that this open source project is simply quite amazing and with regards to enabling data access and preventing people getting ‘Lost in Translation” with regards to using MapServer.

Outside of MapServer I have successfully used the OGR tools with a couple of local authorities to help with scenarios that I am sure many people come across – scheduled replication or dare I say, translation.

1. With OGR and therefore from a command line it is possible to perform SQL statements against datasets when executing.  One example where this is useful is where no actual format translation is required but more that a subset of data needs to be published to the internet (therefore tying in with the topic of data access).  In this scenario we take a MapInfo TAB file of all planning applications since the 1980’s and sub select all the ones that have been applied for this year.  This proves to be very practical if performing operations like Find My Nearest as you may not care about a planning application that was approved when Margaret Thatcher was in power.

2. Another customer had a requirement for creating a layer from some XML that has spatial references at least 3 times a day.  It is actually to be able to show current Roadwork’s.  This has been automated via Windows Scheduled Tasks with the use of OGR.  If anything this saves time and money and provides consistent output without the need of human input.

Obviously this can be seen by some as not being ideal with copies of data being sent around the networks and I agree in a perfect world we may all have large Oracle Spatial Data warehouses but in reality this is not the case whether the constraint be fiscal or honestly just practical.  Personally I follow the KISS principle (Keep It Simple …..)

Integration

Recently on the MUGUKI talk list (the email list for UK MapInfo users) someone asked about accessing  ESRI ArcSDE from MapInfo Professional.  They had a very valid reason.  They had a data cleaning exercise to perform and most of their staff knew MapInfo and not ArcGIS.  Being an advocate of Open Source I suggested using the OGR tool set (www.gdal.org/ogr)  to pull the data out, clean it in MapInfo, and then reload it but it wasn’t feasible.  Although I understand why ArcSDE is a good product with it’s in built multi user editing and version control it does mean that users go back to the old issues of being locked into proprietary formats.

Obviously all of this could have been avoided if things had been stored in a de-facto standard such as Oracle using the SDO format which, as it happens, can be achieved with ArcSDE if you ask for it!. 

Talking about Oracle leads me onto another under used but extremely useful data access technology - Heterogeneous Services.  These are part of the Oracle application suite and can be used within the Spatial Data warehouses.  From my understanding Oracle can create views or virtual tables of data that is held in other databases (i.e. SQL Server, IBM DB2 etc) and have these automatically update etc as defined by the DBA whether on a scheduled basis or on the number of edits that are performed.  With the onset of spatial data warehouses being built on Oracle Spatial this is a great technology to help increase Data Access.

Back to web data access

Most mapping websites are currently using ‘Pull’ technologies for Data Access i.e. the user ‘pulls’ information out by performing actions on a web page.  At Astun we develop a web mapping and data portal called iShareMaps that once installed on a local authority site, allows members of the public to enter their address into the ‘My House’ page and have information literally pulled out from a variety of back office systems such as Roadwork’s specific to the street they live on or which polling station has been assigned to them in an election as well as standard other information such as who is my councillor, closest leisure centre etc.

‘A bit pushy’

We are now moving to allow visitors to these websites to have information ‘pushed’ out to them.  We are terming this as a “Local Alerts” whereby the public can register and then have the alerts pertaining to their area pushed out at scheduled intervals via email.  The typical scenario being that of ‘alert me if any planning applications are within 200m’ – as soon as one appears we notify.  We believe that this is very simple to do but often the most simple things in life are the most useful...

As always I hope that you’ve enjoyed this edition and if you have any questions regarding this or any other edition of Eye on the Web then please do not hesitate to contact me via This e-mail address is being protected from spam bots, you need JavaScript enabled to view it or http://www.isharemaps.com